In recent years, driving assistance apparatuses (called “driving assistance applications” hereinafter) that assist in the driving of a moving vehicle are being developed. For example, lane keeping apparatuses that automatically steers or assist in driving so that vehicles travel along a road, lane departure prevention apparatuses that assist in driving by preventing vehicles from departing from their lanes, emergency avoidance apparatuses that automatically steer vehicles in order to avoid obstructions on the traveled road surface, and so on are being developed.
Request signals outputted from a driving assistance application such as a lane keep apparatus, a lane departure prevention apparatus, or an emergency avoidance apparatus (for example, a signal indicating a target lateral acceleration) are inputted into a lateral momentum control apparatus that controls the lateral momentum (for example, the yaw rate) of the vehicle. Control signals are outputted from this control apparatus to a control target such as an actuator. The lateral momentum of the vehicle is controlled as a result of actuation of the actuator controlled on the basis of the control signals.
The lateral momentum of the vehicle is changed by using various actuators attached to the vehicle. For example, a front steering actuator changes the lateral momentum of the vehicle by turning the front wheels. A rear steering actuator changes the lateral momentum of the vehicle by turning the rear wheels. Further, an actuator for imparting a braking force or a driving force to each wheel individually (DYC actuator) changes the lateral momentum of the vehicle, for example, by imparting a braking force (or a driving force) to the right wheels or the left wheels of the vehicle.
In the case of feedback-controlling the lateral momentum of the vehicle on the basis of the request signal outputted from a certain driving assistance application, the feedback control is performed on the basis of a deviation (difference) between a target lateral momentum and an actual lateral momentum. At this time, in the case of controlling the lateral momentum of the vehicle by using a plurality of actuators, an optimal feedback gain is individually set with respect to each actuator. Thereafter, a feedback control amount is calculated on the basis of the set feedback gain, and each actuator is operated independently on the basis of the calculated feedback control amount.
In the case that the plurality of actuators are actuated independently of each other in order to feedback-control the lateral momentum of the vehicle on the basis of the request signal outputted from the driving assistance application, there is a concern about an actuation interference between the actuators. For example, the following situation can be expected. One actuator is actuated to turn the vehicle to the right and another actuator is actuated to turn the vehicle to the left. When the actuation interference between actuators occurs as described above, the behavior of the vehicle is destabilized.
To cope with this problem, the feedback control amounts of the actuators are not individually determined, but the feedback control amount of the entire control system is determined, and then the determined feedback control amount is distributed to the actuators, thereby preventing the actuation interference between the actuators.
JP2005-299424 A discloses a control apparatus for controlling an output of the controlled object by a plurality of control inputs. According to this control apparatus described in JP2005-299424 A, a plurality of control inputs are individually calculated with sharing one filtering target value, thereby preventing a mutual interference between a plurality of feedback control processes using the plurality of control inputs.